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As in Hypersonic. It looks like the news has just been released about what's being touted as the follow-on to the SR-71 "Blackbird": the SR-72…name to be decided upon later apparently. Sparked by a cover story at Aviation Week, the news is popping up all over, as at the BBC, Defense Tech, WIRED, and elsewhere.

      If nothing else, it appears Lockheed Martin has artwork ready - and a few more details at the company website. With the caption "Speed is the new Stealth", Lockheed Martin is summing up the principle virtue of this design. At Mach 6, it will be faster than any other air-breathing flying machine in the sky, at least twice as fast as the SR-71 Blackbird, now retired. There's nothing that can catch it - or so they expect.

       The mission is straightforward as well: reconnaissance - flying cameras and other sensors over things we want to look at, when we want to look at them. This avoids the problem of waiting for a satellite with the right sensors to orbit overhead at a time when the weather will permit things to be 'seen'. Further, there's discussion of some kind of armaments as an option if some kind of strike is desired.

        The technology is going to be game changing. Lockheed Martin is betting they can successfully build an aircraft around jet engines able to transition from turbines to pure ram jet and back.

The key to the new airplane, as it was with the SR-71, will be the engines. Lockheed Martin told Aviation Week the company has been working with Aerojet Rocketdyne to build an air breathing engine that combines both a traditional turbine and a scramjet to deliver the Mach 6 performance.

Normal turbine jet engines have problems operating at speeds beyond Mach 2. The original SR-71 used a complicated system of a movable nose cone on the engine, along with vents that prevented shockwaves from interfering with the flow, and slowed the air down enough so that it could be ingested by the engine. Though “unstarts” were a regular problem for Blackbird pilots, and caused problems throughout the life of the airplane.

The new SR-72 will use a turbine-based combined cycle (TBCC) that will employ the turbine engine at lower speeds, and use a scramjet at higher speeds. A scramjet engine is designed to operate at hypersonic velocities by compressing the air through a carefully designed inlet, but needs to be traveling supersonic before it is practical to begin with. So far research projects from NASA, the Air Force and other Pentagon entities have not been able to solve the problem of transitioning from the subsonic flight regime, through hypersonic flight with a single aircraft.

(Aviation Week has a detailed set of graphics with the cover story.)

Further, they're betting they can build an airframe able to stand the high temperatures air friction will create, and with the range to make it worthwhile. And what's more it will be automated - a drone with no one on board. This actually makes some things simpler - keeping mere humans alive under the conditions this aircraft is intended to experience would add a lot of weight and complicated systems to the design.


The proposal is exciting, if only for the way it promises to advance the state of the art. BUT… even a prototype is several years away, and until hardware actually starts flying, there's no way to be sure Lockheed Martin will be able to make it work. They claim they have enough work done showing it is both practical AND affordable to begin work. There's a lot of experimental research into hypersonic aircraft, but to the best of my knowledge, actual flight time with working models is more commonly measured in minutes or even seconds - not the hours a working SR-72 will be expected to fly. Mach 6 is actually not as ambitious as some of the experimental programs have explored, so it's possible they're not kidding.

Further, costs are only estimates at this time. The real world usually ends up being a lot more expensive, if only because there are things you can only find out once you start trying to do this kind of thing for real. Future budget constraints or other programs could cannibalize this down the road.

And, the problem of operating an aircraft like this with no one on board poses special challenges. Lockheed Martin is talking about building a technology demonstrator that will have a pilot. I'm guessing the production aircraft is going to have to be much more autonomous than the sort of subsonic drones currently making up the bulk of the drone fleet. For one, there simply wouldn't be time for a pilot operating over a comm link to react to problems, not at the speeds the aircraft will be flying. (In fact, it's a question of whether or not any human would be able to fly this even if they were riding inside a cockpit without a lot of computer support to keep the aircraft "within the envelope.") For another, reliance on external signals (i.e.: command inputs from a remote operator, signals from navsats) are vulnerable to interference or even 'spoofing'.

Given how the SR-72 will be optimized for hypersonic speed, it's a bit much to expect it to be easy to fly at low speed for landing, and takeoff will be exciting. Lockheed Martin claims they've got the low speed end of the flight envelope within practical limits. Refueling it in flight - with no one on board - will not be a piece of cake either.

I'm speculating here, but it would make sense to me if the SR-72 ended up being carried aloft and launched in the air by a specialized larger plane. It wouldn't need to burn fuel to reach altitude, and it would make basing it a lot more flexible if the mothership could do the tedious work of flying the long routes needed to get it in position for a run. Recovering it afterwards would be… interesting to say the least. If it can be recovered in the air as well, it would not need to carry landing gear at all. And that's a fair amount of weight saved right there.

The Air Force has a lot of interest in this aircraft, if only because the technology needed to make it work will be essential for a proposed new manned bomber to enter service some point down the road in this century, because A) there will be no more new B-52s, B-1s, or B-2s - and B) their capabilities will no longer be match what the Air Force may need to do… whatever that may be.

(And before reflexive military bashing on spending can kick in, let me observe the Air Force will need something - because the current fleet will eventually wear out, and any kind of replacement is going to take years to develop, whatever it is. They always have to be thinking ahead - it's part of their job.)

I have several other things to offer for consideration on this. For one, the British seem to be pretty enthused about the SABRE engine, which also promises a revolution in aircraft design, one with a lot more potential than the Lockheed Martin proposal. An air-breathing rocket engine could make near space/LEO a lot easier to reach, and far more routine than at present. That too will be a game changer - and the British seem to be a lot farther ahead at the moment.

The X-37B program is another. A reusable robot spaceplane, it theoretically could be launched quickly, and could carry a variety of sensor packages for different missions. It can change its orbit, stay there for months, and land like an airplane. It's possible to see a fleet of these tasked with doing those critical reconn missions proposed for the SR-72, almost on-demand. They could not, however, launch any kind of strike from space - if only because of all the treaty problems this would cause.

Finally, there's one more thing that puzzles me. Why is all this SR-72 news taking place out in the open? Traditionally, these kinds of capabilities are developed in secret and kept secret for as long as possible. This news is giving the kind of 'targets' this aircraft might be used on a lot of lead time to start developing counter-measures. (Indeed, there are rumors the Air Force has already been operating a hypersonic aircraft in secret for some time now.)

Whatever happens, it will be some time before an SR-72 flies - if ever. Meanwhile, here's a BBC story on what it was like to fly the SR-71 - and another on the depressingly unlikely odds that a Concorde will ever fly again.

ADDENDUM: There's been some discussion in comments asking why we would need this aircraft when we have satellites. Well, as has been noted, it can take time before a satellite's orbit puts it in the right place at the right time and with the right weather to see something we badly want to see. The SR-72 could respond in hours, not days or weeks.

Further, there's another consideration. The kind of satellites that can give the clearest picture are in relatively low orbits - which means they are vulnerable to attacks that can take them out of action. (The Chinese have demonstrated this capability, for example.) If we rely primarily on satellites for critical information and other capabilities, they'd be the first targets of a serious offensive. We do not (as far as I know) have the capability to replace them with anything short of months or even years if they get knocked out. (Near-earth space orbitals would also become a lot less survivable for any satellites, with spreading orbital debris clouds. The movie Gravity makes this pretty clear, I understand.)

A hypersonic reconn aircraft would A) give us redundant surveillance capabilities that B) could be deployed more rapidly, and C) reduce the incentive to knock out satellites. Such an attack would in itself give pretty obvious indication that something was up - and with less to gain from it, it would be less useful for an adversary to attack in the first place.

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Comment Preferences

  •  Tip Jar (17+ / 0-)

    Higher, farther, faster - that's always been the goal in aviation. And if we can add smarter and cheaper to the mix, that wouldn't be bad either.

    "No special skill, no standard attitude, no technology, and no organization - no matter how valuable - can safely replace thought itself."

    by xaxnar on Tue Nov 05, 2013 at 06:26:24 AM PST

  •  I enjoy these diaries. (5+ / 0-)

    A good friend and former roommate of mine was a commercial pilot and got me hooked on aviation. I am not a pilot myself, but I learned a lot about flying from him and a greater appreciation for what it takes to get anything off the ground.

  •  I'm actually surprised we don't have one already (11+ / 0-)

    The SR-71 was built with late 1950s technology by people using slide rules and drafting tables.

    The two main problems are:

    Propulsion - which it sounds like they have under control.

    Materials - many aircraft the could otherwise have gone faster were limited by skin temperature. Go too fast and things start melting.

    If the pilot's good, see, I mean if he's reeeally sharp, he can barrel that baby in so low... oh you oughta see it sometime. It's a sight. A big plane like a '52... varrrooom! Its jet exhaust... frying chickens in the barnyard!

    by Major Kong on Tue Nov 05, 2013 at 06:45:18 AM PST

  •  This sounds like one of those projects where (2+ / 0-)
    Recommended by:
    CFAmick, Jay C

    some defense contractor promises STAR WARS technology is you'll just give them a billion dollars and 10 years to make it work. Then 10 billion dollars and 25 years later it turns out, oops, it doesnt work. But yet another CEO gets to retire to his own private island and some other schmuck in the corner office starts the cycle all over again.

  •  Lasers are fast enough to catch most things. (2+ / 0-)
    Recommended by:
    Uncle Cosmo, blue aardvark

    And we've put a lot of research into them as have the Russians.

    Better have a plan for dealing with THAT, too.

    Similar problem to the heating one, but in this case sensors (and pilots, if any) can be blinded.

    Happy little moron, Lucky little man.
    I wish I was a moron, MY GOD, Perhaps I am!
    —Spike Milligan

    by polecat on Tue Nov 05, 2013 at 07:54:50 AM PST

  •  Yeah, that was my thought too.... (2+ / 0-)
    Recommended by:
    xaxnar, RiveroftheWest

    Soon as I read one of those articles I thought "Hmmm.. how about strapping a SABRE to that thing?"

    I've been following the news from Reaction Engines and the SABRE looks like an extremely well thought out project. It will, of course, take time but the initial technology demonstrations have gone very well indeed.

  •  human pilots really are now the limiting factor in (4+ / 0-)
    And what's more it will be automated - a drone with no one on board. This actually makes some things simpler - keeping mere humans alive under the conditions this aircraft is intended to experience would add a lot of weight and complicated systems to the design.
    high-tech aviation.  I think it not at all impossible that the current generation of military aircraft are the last that will have pilots, and remotely-piloted vehicles will be the future of military aviation.

    In the end, reality always wins.

    by Lenny Flank on Tue Nov 05, 2013 at 08:49:52 AM PST

  •  Blockhead-Moron shilling for more tax $$ (0+ / 0-)

    I love this part from the B-M website:

    A hypersonic plane does not have to be an expensive, distant possibility.  In fact, an SR-72 could be operational by 2030.
    16+ years from now is not "a distant possibility"--? Particularly since that assumes that everything goes letter-perfect, which it never does?? Do those overcredentialed imbeciles expect that no one out here can count??? Or do they think everyone will just murmur Ooooh, speedy--????

    By 2030 I would expect that even small nations will be able to afford the latest in high-powered laser defense systems--whose beams travel roughly 186,300 times faster than the SR-72 Boondoggle ever will.

    This atrocity is designed to do exactly one thing: Fatten the bank accounts of Blockhead-Moron top execs, stockholders, and engineers, in that order.

    The greatest trick the GOP ever played was convincing the devil they had a soul to sell.

    by Uncle Cosmo on Tue Nov 05, 2013 at 09:19:51 AM PST

    •  I think you are entirely correct . . . though (1+ / 0-)
      Recommended by:
      Roger Fox

      it does sound like very interesting technology.

      In the end, reality always wins.

      by Lenny Flank on Tue Nov 05, 2013 at 09:43:59 AM PST

      [ Parent ]

      •  Any technology that promotes SSTO (0+ / 0-)

        is interesting technology in my book. But this Rube Goldberg engine only gets to Mach 6 when Mach 25 is what's needed. The SABRE engine is much more exciting--& not being developed to kill or spy on other folks.

        The greatest trick the GOP ever played was convincing the devil they had a soul to sell.

        by Uncle Cosmo on Tue Nov 05, 2013 at 11:29:24 AM PST

        [ Parent ]

    •  I think you are missing a couple of things (1+ / 0-)
      Recommended by:

      1) lasers have to be aimed
      2) Something traveling at Mach 6 goes horizon to horizon quickly

      At 100,000 feet (30,000 meters) the horizon is about 350 km or 350,000 meters. The speed of sound at that height is about 300 m/s. Mach 6, then, is 1800 m/s.

      The SR-72 will go horizon to horizon in 350,000/1,800 = 194 seconds or a little more than three minutes.

      Not only will poor countries be shooting this down with lasers, extremely rich and powerful countries will also not be shooting this down with lasers. The biggest lasers are chemical pulse lasers and those fire short pulses, which means aim has to be perfect.

      Lasers which can "track" the plane deliver much less energy per second.

      All the plane has to do is vary its course slightly as it flies rather than following a convenient  straight line, plus adding some stealth to make it take longer for radars to get a lock, and you've got a plane that can overfly Moscow or Beijing.

      I'm on a mission! Testing the new site rules.

      by blue aardvark on Tue Nov 05, 2013 at 10:01:23 AM PST

      [ Parent ]

      •  Not perfect by a long shot (0+ / 0-)

        Wing that dingus anywhere & its own KE will turn it into pricey junk in a twinkle.

        At least they won't have a 21st-century Francis Gary Powers for a show trial.

        All the SR-72 Boondoggle will do is force actors doing things they don't want us to see to implement better maskirovka--which will no doubt be a lot cheaper than the Boondoggle.

        Classic example of defense spending as welfare for overcredentialed engineers who've never outgrown the juvenile sugar-high of making things go zoom & blowing shit up.

        The greatest trick the GOP ever played was convincing the devil they had a soul to sell.

        by Uncle Cosmo on Tue Nov 05, 2013 at 11:25:13 AM PST

        [ Parent ]

        •  Yes, of course, a tiny hit (0+ / 0-)

          means it's kinetic energy acts against it.


          You keep using technical terms. I do not think they mean what you think they mean.

          I'm on a mission! Testing the new site rules.

          by blue aardvark on Tue Nov 05, 2013 at 11:47:25 AM PST

          [ Parent ]

          •  "A tiny hit" that damages the aerodynamics (0+ / 0-)

            enough to cause any sort of wobble at 3600 mph will turn the thing into tumbling junk. Did you seriously think I meant something more drastic?

            The greatest trick the GOP ever played was convincing the devil they had a soul to sell.

            by Uncle Cosmo on Tue Nov 05, 2013 at 03:28:01 PM PST

            [ Parent ]

            •  Lasers don't transmit force (0+ / 0-)

              They transmit heat. The momentum of the photons is insignificant to a craft of any size.

              Or are you now firing AA guns at a mach 6 craft 30 km above the earth? Do you seriously propose to fire dozens (hundreds? thousands?) of shells into the air at various heights and places in hopes one of them puts a piece of shrapnel into the spy plane? With, remember, about one minute's warning?

              A plane which is faster than the SAM missile is not going to be shot down by said missile, no?

              What is exerting this tiny force?

              And given aerodynamic buffeting, yes, the plane will be designed with control authority sufficient that a tiny hit will not cause it to tumble. There are always forces acting on a plane in flight other than thrust and gravity. Did you think there was no wind at altitude?

              How much force do you think a downdraft of, say, 5 MPH exerts on the entire upper surface of a large plane? Clue: more than a "tiny" amount. Do you honestly think LM can't design a plane that could handle a 5 MPH downdraft in flight? Seriously?

              I'm on a mission! Testing the new site rules.

              by blue aardvark on Wed Nov 06, 2013 at 06:30:51 AM PST

              [ Parent ]

  •  Revisit times are always a concern (1+ / 0-)
    Recommended by:

    for satellites. A LEO bird will orbit the earth about once ever 90 minutes to 2 hours, depending on how low the LEO is. Depending on the orbit, the latitude of the ascending node will precess, and thus it may be hours or days before it passes over another point again.

    The easy way to ameliorate this problem is multiple satellites. The second way is being able to point a sensor "sideways". If the sensor needs sunlight to work, though, you can't do much in the part of the orbit that's in the dark.

    So, yes, this sounds useful.

    The old SR-71 birds used to drip fuel onto the tarmac before flight because the amount of space required for thermal expansion in flight left loose seals when the wings were cold. That would argue against picking the plane up and launching it with from a mother ship, because you've got leaking fuel attached to your mother.

    I'm on a mission! Testing the new site rules.

    by blue aardvark on Tue Nov 05, 2013 at 09:43:34 AM PST

    •  Unless... (3+ / 0-)

      The mothership doesn't fuel it until just before it's ready to launch. They can do the pre-launch checks before committing to fueling it all the way - and the closer they get it, the less fuel it needs for it's mission.

      "No special skill, no standard attitude, no technology, and no organization - no matter how valuable - can safely replace thought itself."

      by xaxnar on Tue Nov 05, 2013 at 10:04:14 AM PST

      [ Parent ]

  •  Let's not forget the X-37b (2+ / 0-)
    Recommended by:
    RiveroftheWest, Otteray Scribe

    The super secret Air Force mini-shuttle who's mission still hasn't been announced - but who can doubt spying is a major part of it?

    There are really only 10 kinds of people in this world; those who understand Binary, and those who don't.

    by Fordmandalay on Tue Nov 05, 2013 at 10:07:11 AM PST

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